ntpdate problem

[RW]

On Sat, 13 Mar 2010 18:03:42 +0000
Matthew Seaman <m.seaman at infracaninophile.co.uk> wrote:

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> On 13/03/2010 14:47:31, Антон Клесс wrote:
> > I saw that more than year ago on my teacher's server, when I was
> > deal with my first FreeBSD, so it's just a kind of habit.
> 
> It's a bad habit you should try and cure yourself of.  Stepping the
> clock with ntpdate(8) can cause nasty effects like time apparently
> going backwards -- and that will seriously upset a lot of software.
> 
> Also, it doesn't account for the natural clock drift of your system,
> so it's going to give you pretty terrible accuracy -- probably good
> to no more than a few seconds.  ntpdate(8) is really only intended to
> get the clock into the right ballpark at system boot so that ntpd(8)
> has a fighting chance of getting into synch.  The NTP project has
> deprecated ntpdate(8) for some time now, and instead prefers adding
> an option to ntpd(8) to say "set the clock on initial startup no
> matter how far out it is."
> 
> > But on the other hand, if it exists, it could work properly, and I
> > am interested in just to understand, how it should be set up.
> 
> I'm assuming you're on some sort of always-on network, like ADSL?
> Most people are nowadays.  In which case, there's really no reason
> not to run ntpd(8) the way it is intended to be used.
> 
> Just add the following to /etc/rc.conf:
> 
> ntpd_enable="YES"
> ntpd_sync_on_start="YES"
> 



  ntpd_sync_on_start="YES"

is not a complete substitute for running ntpdate at startup. It allows
ntpd to make a large correction, but it doesn't block the boot sequence
so you could still get a large step-change later-on when your daemons
are starting-up. 

ntpd has an option to emulate ntpdate, but it holds-up the
boot-sequence much longer - presumably this is why ntpdate has been
deprecated for a long time but hasn't yet gone away. 

you can run ntpdate at boot with

   ntpdate_enable=YES

the rc script gets the servers from ntp.conf